Could anyone say what would be the price range for different nitropropenes (for example 1-phenyl-2-nitropropene and 2,5-dimethoxyphenyl-2-nitropropene)?

I'm just curious; haven't seen any nitropropenes on the sale...  

Look harder.  Smart bees pay tax on their loot.

Common pricing for nitrostyrenes from Aldrich/Alfa/Lancaster etc is around $100/10g, but they won't sell you anything interesting without a fight...

True. When I was running some tests with gamma-valerolactone, I had to fight a month to get it from
Aldrich even that I had all the permits and end user statements..

Prices should be around 1000-1500 euro/kg for 1-phenyl-2-nitropropene and 2000-3000 euro/kg for the substituted ones, like 1-(2,5-dimethoxyphenyl)-2-nitropropene, unless the starting aldehyde is extremly expensive.